1. Field of the Invention
The present invention relates to the field of computer graphics systems. More specifically, the present invention relates to the use of parametric texture maps to model a scene under varying focus conditions
2. Related Art
Photographs provide a two-dimensional representation of a three dimensional scene as captured by an imaging device, such as a camera. A skilled photographer can manipulate the imaging device by varying focus parameters to produce different photographs of the same scene. Since there is no single representation of a scene, the art of photography involves knowing how to manipulate an imaging device to create the desired photographic representation.
Although the term xe2x80x9cphotographxe2x80x9d is used throughout this disclosure, the term, photograph, is not limited to conventional film based or digital means, but is directed towards all means of capturing images.
Heretofore, once a photograph was created, pre-production parameters used to create the photograph could not be changed. For example, focus conditions in one or more dimensions were pre-designated in the imaging device at the time of exposure in order to create the photograph. These various dimensions include focus conditions that vary in focus depth, depth of field, etc.
Unfortunately, the photograph in the prior art was dictated by the focus conditions set by the imaging device. Thus, the focus condition of the photograph was fixed and determined at the time of exposure. Once fixed, after the exposure, the photographer had no control over the focus conditions in the post production process.
For example, in an advertising campaign, a photoshoot of a static three-dimensional scene having distinct foreground and background areas is conducted. The photographer may take numerous photos at varying focus conditions in two dimensions: focal depth and depth of field. Thereafter, the photographer produces a photo-layout of the scene with photographs of varying focus conditions. Depending on the skill of the photographer, it is hoped that at least one of the photographs in the photo-layout can be used in the advertising campaign.
During the photoshoot, the photographer is limited by time, expense, and practicality. In other words, the photographer cannot take photographs over the full range of focus conditions. This is where the photographer""s skill and knowledge in the art of photography are utilized. Through experience, the photographer selects the focus conditions necessary to produce a particular photograph for the photo-layout and ultimately for the advertising campaign.
However, for each of the photographs created, the focus conditions are unchangeable. Should the photographer discover that a desired photograph, not in the photo-layout, would best represent the advertising campaign, then the photographer could not create that desired photograph in the post-production process. Instead, the photographer would have to recreate the conditions in the original photo-shoot and retake the photograph using the specific focal depth and depth of field that is associated with the desired focus condition needed.
Depending on the set-up, the particular realistic scene may or may not be able to be practically recreated. In a landscape scene, the particular condition at the original photoshoot, such as a lightning storm at sunset, may not exist. At other times, a manufactured set-up may be overly expensive and difficult to recreate. In either case, the desired photograph cannot be created without additional expense, time, and energy.
A photoshoot is conducted by a photographer skilled in the art of photography: normally a professional photographer. The professional, through years of experience and learning, can manipulate the imaging device to produce the desired focus effects (e.g., focus depth and depth of field). An amateur photographer, on the other hand, may not be skilled enough in photography to understand how focus conditions will affect the created photograph. Usually, the amateur photographer relies on the imaging device to automatically determine the exposure and select the focus parameters to effect the exposure. The imaging device may or may not produce a photograph having a desired focus condition.
For example, in a landscape photograph, the photographer may desire to have the foreground and the background in sharp focus. This would require an exposure having, among other parameters, an aperture on the lens of the imaging device giving a wider depth of field. However, the imaging device may have automatically set up the exposure with an aperture giving a shallow depth of field. As a result, the produced photograph will not give the desired wider depth of field.
Thus, a need exists for a process where pre-production decisions in creating photographs do not necessarily control and limit post-production photographs. Another need exists for a photographic process that compensates for the lack of knowledge in the area of focus effects exhibited by an amateur photographer.
The present invention provides a method for varying focus in photographs of a scene. One embodiment of the present invention provides a method that achieves the above accomplishment and which also provides for control over focus parameters at any point in the production process. Additionally, one embodiment of the present invention provides a method that achieves the above accomplishments and which also provides for a photographic process that compensates for the lack of skill by an amateur photographer in selecting focus parameters.
Specifically, one embodiment of the present invention discloses a method for modeling a scene using a parametric texture map (PTM) under varying focus conditions of one or more dimensions: e.g., focus depth and depth of field. A dataset of photographs is obtained under separate focus conditions. Performing an approximation of the dataset allows for the capability to generate a spectrum of photographs of the scene. The spectrum of photographs represent varying focus conditions anywhere within a range of focus conditions specified by the initial dataset of photographs. In addition, extrapolation yields results outside the range of focus conditions.
These and other benefits of the present invention will no doubt become obvious to those of ordinary skill in the art after having read the following detailed description of the preferred embodiments which are illustrated in the various drawing figures.